1. Technical Field
Example embodiments relate to a semiconductor device and a method of manufacturing the same.
2. Description of the Related Art
Transistors are commonly used as switching devices or driving devices in electronic devices. A thin film transistor can be formed on a glass substrate or a plastic substrate. As a result, thin film transistors are often used in flat panel display apparatuses (e.g., liquid crystal display apparatuses, organic light-emitting display apparatuses).
To increase the operational characteristic of a transistor, attempts have been made to utilize an oxide layer (e.g., ZnO-based layer having a high carrier mobility) as a channel layer of the transistor. This conventional method is mainly employed for manufacturing thin film transistors for flat panel display apparatuses. However, the threshold voltage is difficult to control in a transistor having an oxide layer as the channel layer (e.g., conventional oxide transistor).
A conventional oxide transistor mainly uses an n-type oxide layer as the channel layer. To obtain a high ON/OFF current ratio and a small subthreshold slope (S.S.), the n-type oxide layer must have a high carrier concentration and a high crystallinity. To control the threshold voltage, if the carrier concentration of the n-type oxide layer is reduced, the ON/OFF current ratio is reduced and the subthreshold slope (S.S.) is increased, thus degrading the operational characteristics of the transistor.